1 /* 2 * Request reply cache. This is currently a global cache, but this may 3 * change in the future and be a per-client cache. 4 * 5 * This code is heavily inspired by the 44BSD implementation, although 6 * it does things a bit differently. 7 * 8 * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de> 9 */ 10 11 #include <linux/slab.h> 12 #include <linux/sunrpc/addr.h> 13 #include <linux/highmem.h> 14 #include <linux/log2.h> 15 #include <linux/hash.h> 16 #include <net/checksum.h> 17 18 #include "nfsd.h" 19 #include "cache.h" 20 21 #define NFSDDBG_FACILITY NFSDDBG_REPCACHE 22 23 /* 24 * We use this value to determine the number of hash buckets from the max 25 * cache size, the idea being that when the cache is at its maximum number 26 * of entries, then this should be the average number of entries per bucket. 27 */ 28 #define TARGET_BUCKET_SIZE 64 29 30 struct nfsd_drc_bucket { 31 struct list_head lru_head; 32 spinlock_t cache_lock; 33 }; 34 35 static struct nfsd_drc_bucket *drc_hashtbl; 36 static struct kmem_cache *drc_slab; 37 38 /* max number of entries allowed in the cache */ 39 static unsigned int max_drc_entries; 40 41 /* number of significant bits in the hash value */ 42 static unsigned int maskbits; 43 static unsigned int drc_hashsize; 44 45 /* 46 * Stats and other tracking of on the duplicate reply cache. All of these and 47 * the "rc" fields in nfsdstats are protected by the cache_lock 48 */ 49 50 /* total number of entries */ 51 static atomic_t num_drc_entries; 52 53 /* cache misses due only to checksum comparison failures */ 54 static unsigned int payload_misses; 55 56 /* amount of memory (in bytes) currently consumed by the DRC */ 57 static unsigned int drc_mem_usage; 58 59 /* longest hash chain seen */ 60 static unsigned int longest_chain; 61 62 /* size of cache when we saw the longest hash chain */ 63 static unsigned int longest_chain_cachesize; 64 65 static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec); 66 static void cache_cleaner_func(struct work_struct *unused); 67 static unsigned long nfsd_reply_cache_count(struct shrinker *shrink, 68 struct shrink_control *sc); 69 static unsigned long nfsd_reply_cache_scan(struct shrinker *shrink, 70 struct shrink_control *sc); 71 72 static struct shrinker nfsd_reply_cache_shrinker = { 73 .scan_objects = nfsd_reply_cache_scan, 74 .count_objects = nfsd_reply_cache_count, 75 .seeks = 1, 76 }; 77 78 /* 79 * locking for the reply cache: 80 * A cache entry is "single use" if c_state == RC_INPROG 81 * Otherwise, it when accessing _prev or _next, the lock must be held. 82 */ 83 static DECLARE_DELAYED_WORK(cache_cleaner, cache_cleaner_func); 84 85 /* 86 * Put a cap on the size of the DRC based on the amount of available 87 * low memory in the machine. 88 * 89 * 64MB: 8192 90 * 128MB: 11585 91 * 256MB: 16384 92 * 512MB: 23170 93 * 1GB: 32768 94 * 2GB: 46340 95 * 4GB: 65536 96 * 8GB: 92681 97 * 16GB: 131072 98 * 99 * ...with a hard cap of 256k entries. In the worst case, each entry will be 100 * ~1k, so the above numbers should give a rough max of the amount of memory 101 * used in k. 102 */ 103 static unsigned int 104 nfsd_cache_size_limit(void) 105 { 106 unsigned int limit; 107 unsigned long low_pages = totalram_pages - totalhigh_pages; 108 109 limit = (16 * int_sqrt(low_pages)) << (PAGE_SHIFT-10); 110 return min_t(unsigned int, limit, 256*1024); 111 } 112 113 /* 114 * Compute the number of hash buckets we need. Divide the max cachesize by 115 * the "target" max bucket size, and round up to next power of two. 116 */ 117 static unsigned int 118 nfsd_hashsize(unsigned int limit) 119 { 120 return roundup_pow_of_two(limit / TARGET_BUCKET_SIZE); 121 } 122 123 static u32 124 nfsd_cache_hash(__be32 xid) 125 { 126 return hash_32(be32_to_cpu(xid), maskbits); 127 } 128 129 static struct svc_cacherep * 130 nfsd_reply_cache_alloc(void) 131 { 132 struct svc_cacherep *rp; 133 134 rp = kmem_cache_alloc(drc_slab, GFP_KERNEL); 135 if (rp) { 136 rp->c_state = RC_UNUSED; 137 rp->c_type = RC_NOCACHE; 138 INIT_LIST_HEAD(&rp->c_lru); 139 } 140 return rp; 141 } 142 143 static void 144 nfsd_reply_cache_free_locked(struct svc_cacherep *rp) 145 { 146 if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) { 147 drc_mem_usage -= rp->c_replvec.iov_len; 148 kfree(rp->c_replvec.iov_base); 149 } 150 list_del(&rp->c_lru); 151 atomic_dec(&num_drc_entries); 152 drc_mem_usage -= sizeof(*rp); 153 kmem_cache_free(drc_slab, rp); 154 } 155 156 static void 157 nfsd_reply_cache_free(struct nfsd_drc_bucket *b, struct svc_cacherep *rp) 158 { 159 spin_lock(&b->cache_lock); 160 nfsd_reply_cache_free_locked(rp); 161 spin_unlock(&b->cache_lock); 162 } 163 164 int nfsd_reply_cache_init(void) 165 { 166 unsigned int hashsize; 167 unsigned int i; 168 int status = 0; 169 170 max_drc_entries = nfsd_cache_size_limit(); 171 atomic_set(&num_drc_entries, 0); 172 hashsize = nfsd_hashsize(max_drc_entries); 173 maskbits = ilog2(hashsize); 174 175 status = register_shrinker(&nfsd_reply_cache_shrinker); 176 if (status) 177 return status; 178 179 drc_slab = kmem_cache_create("nfsd_drc", sizeof(struct svc_cacherep), 180 0, 0, NULL); 181 if (!drc_slab) 182 goto out_nomem; 183 184 drc_hashtbl = kcalloc(hashsize, sizeof(*drc_hashtbl), GFP_KERNEL); 185 if (!drc_hashtbl) 186 goto out_nomem; 187 for (i = 0; i < hashsize; i++) { 188 INIT_LIST_HEAD(&drc_hashtbl[i].lru_head); 189 spin_lock_init(&drc_hashtbl[i].cache_lock); 190 } 191 drc_hashsize = hashsize; 192 193 return 0; 194 out_nomem: 195 printk(KERN_ERR "nfsd: failed to allocate reply cache\n"); 196 nfsd_reply_cache_shutdown(); 197 return -ENOMEM; 198 } 199 200 void nfsd_reply_cache_shutdown(void) 201 { 202 struct svc_cacherep *rp; 203 unsigned int i; 204 205 unregister_shrinker(&nfsd_reply_cache_shrinker); 206 cancel_delayed_work_sync(&cache_cleaner); 207 208 for (i = 0; i < drc_hashsize; i++) { 209 struct list_head *head = &drc_hashtbl[i].lru_head; 210 while (!list_empty(head)) { 211 rp = list_first_entry(head, struct svc_cacherep, c_lru); 212 nfsd_reply_cache_free_locked(rp); 213 } 214 } 215 216 kfree (drc_hashtbl); 217 drc_hashtbl = NULL; 218 drc_hashsize = 0; 219 220 if (drc_slab) { 221 kmem_cache_destroy(drc_slab); 222 drc_slab = NULL; 223 } 224 } 225 226 /* 227 * Move cache entry to end of LRU list, and queue the cleaner to run if it's 228 * not already scheduled. 229 */ 230 static void 231 lru_put_end(struct nfsd_drc_bucket *b, struct svc_cacherep *rp) 232 { 233 rp->c_timestamp = jiffies; 234 list_move_tail(&rp->c_lru, &b->lru_head); 235 schedule_delayed_work(&cache_cleaner, RC_EXPIRE); 236 } 237 238 static long 239 prune_bucket(struct nfsd_drc_bucket *b) 240 { 241 struct svc_cacherep *rp, *tmp; 242 long freed = 0; 243 244 list_for_each_entry_safe(rp, tmp, &b->lru_head, c_lru) { 245 /* 246 * Don't free entries attached to calls that are still 247 * in-progress, but do keep scanning the list. 248 */ 249 if (rp->c_state == RC_INPROG) 250 continue; 251 if (atomic_read(&num_drc_entries) <= max_drc_entries && 252 time_before(jiffies, rp->c_timestamp + RC_EXPIRE)) 253 break; 254 nfsd_reply_cache_free_locked(rp); 255 freed++; 256 } 257 return freed; 258 } 259 260 /* 261 * Walk the LRU list and prune off entries that are older than RC_EXPIRE. 262 * Also prune the oldest ones when the total exceeds the max number of entries. 263 */ 264 static long 265 prune_cache_entries(void) 266 { 267 unsigned int i; 268 long freed = 0; 269 bool cancel = true; 270 271 for (i = 0; i < drc_hashsize; i++) { 272 struct nfsd_drc_bucket *b = &drc_hashtbl[i]; 273 274 if (list_empty(&b->lru_head)) 275 continue; 276 spin_lock(&b->cache_lock); 277 freed += prune_bucket(b); 278 if (!list_empty(&b->lru_head)) 279 cancel = false; 280 spin_unlock(&b->cache_lock); 281 } 282 283 /* 284 * Conditionally rearm the job to run in RC_EXPIRE since we just 285 * ran the pruner. 286 */ 287 if (!cancel) 288 mod_delayed_work(system_wq, &cache_cleaner, RC_EXPIRE); 289 return freed; 290 } 291 292 static void 293 cache_cleaner_func(struct work_struct *unused) 294 { 295 prune_cache_entries(); 296 } 297 298 static unsigned long 299 nfsd_reply_cache_count(struct shrinker *shrink, struct shrink_control *sc) 300 { 301 return atomic_read(&num_drc_entries); 302 } 303 304 static unsigned long 305 nfsd_reply_cache_scan(struct shrinker *shrink, struct shrink_control *sc) 306 { 307 return prune_cache_entries(); 308 } 309 /* 310 * Walk an xdr_buf and get a CRC for at most the first RC_CSUMLEN bytes 311 */ 312 static __wsum 313 nfsd_cache_csum(struct svc_rqst *rqstp) 314 { 315 int idx; 316 unsigned int base; 317 __wsum csum; 318 struct xdr_buf *buf = &rqstp->rq_arg; 319 const unsigned char *p = buf->head[0].iov_base; 320 size_t csum_len = min_t(size_t, buf->head[0].iov_len + buf->page_len, 321 RC_CSUMLEN); 322 size_t len = min(buf->head[0].iov_len, csum_len); 323 324 /* rq_arg.head first */ 325 csum = csum_partial(p, len, 0); 326 csum_len -= len; 327 328 /* Continue into page array */ 329 idx = buf->page_base / PAGE_SIZE; 330 base = buf->page_base & ~PAGE_MASK; 331 while (csum_len) { 332 p = page_address(buf->pages[idx]) + base; 333 len = min_t(size_t, PAGE_SIZE - base, csum_len); 334 csum = csum_partial(p, len, csum); 335 csum_len -= len; 336 base = 0; 337 ++idx; 338 } 339 return csum; 340 } 341 342 static bool 343 nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp) 344 { 345 /* Check RPC XID first */ 346 if (rqstp->rq_xid != rp->c_xid) 347 return false; 348 /* compare checksum of NFS data */ 349 if (csum != rp->c_csum) { 350 ++payload_misses; 351 return false; 352 } 353 354 /* Other discriminators */ 355 if (rqstp->rq_proc != rp->c_proc || 356 rqstp->rq_prot != rp->c_prot || 357 rqstp->rq_vers != rp->c_vers || 358 rqstp->rq_arg.len != rp->c_len || 359 !rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) || 360 rpc_get_port(svc_addr(rqstp)) != rpc_get_port((struct sockaddr *)&rp->c_addr)) 361 return false; 362 363 return true; 364 } 365 366 /* 367 * Search the request hash for an entry that matches the given rqstp. 368 * Must be called with cache_lock held. Returns the found entry or 369 * NULL on failure. 370 */ 371 static struct svc_cacherep * 372 nfsd_cache_search(struct nfsd_drc_bucket *b, struct svc_rqst *rqstp, 373 __wsum csum) 374 { 375 struct svc_cacherep *rp, *ret = NULL; 376 struct list_head *rh = &b->lru_head; 377 unsigned int entries = 0; 378 379 list_for_each_entry(rp, rh, c_lru) { 380 ++entries; 381 if (nfsd_cache_match(rqstp, csum, rp)) { 382 ret = rp; 383 break; 384 } 385 } 386 387 /* tally hash chain length stats */ 388 if (entries > longest_chain) { 389 longest_chain = entries; 390 longest_chain_cachesize = atomic_read(&num_drc_entries); 391 } else if (entries == longest_chain) { 392 /* prefer to keep the smallest cachesize possible here */ 393 longest_chain_cachesize = min_t(unsigned int, 394 longest_chain_cachesize, 395 atomic_read(&num_drc_entries)); 396 } 397 398 return ret; 399 } 400 401 /* 402 * Try to find an entry matching the current call in the cache. When none 403 * is found, we try to grab the oldest expired entry off the LRU list. If 404 * a suitable one isn't there, then drop the cache_lock and allocate a 405 * new one, then search again in case one got inserted while this thread 406 * didn't hold the lock. 407 */ 408 int 409 nfsd_cache_lookup(struct svc_rqst *rqstp) 410 { 411 struct svc_cacherep *rp, *found; 412 __be32 xid = rqstp->rq_xid; 413 u32 proto = rqstp->rq_prot, 414 vers = rqstp->rq_vers, 415 proc = rqstp->rq_proc; 416 __wsum csum; 417 u32 hash = nfsd_cache_hash(xid); 418 struct nfsd_drc_bucket *b = &drc_hashtbl[hash]; 419 unsigned long age; 420 int type = rqstp->rq_cachetype; 421 int rtn = RC_DOIT; 422 423 rqstp->rq_cacherep = NULL; 424 if (type == RC_NOCACHE) { 425 nfsdstats.rcnocache++; 426 return rtn; 427 } 428 429 csum = nfsd_cache_csum(rqstp); 430 431 /* 432 * Since the common case is a cache miss followed by an insert, 433 * preallocate an entry. 434 */ 435 rp = nfsd_reply_cache_alloc(); 436 spin_lock(&b->cache_lock); 437 if (likely(rp)) { 438 atomic_inc(&num_drc_entries); 439 drc_mem_usage += sizeof(*rp); 440 } 441 442 /* go ahead and prune the cache */ 443 prune_bucket(b); 444 445 found = nfsd_cache_search(b, rqstp, csum); 446 if (found) { 447 if (likely(rp)) 448 nfsd_reply_cache_free_locked(rp); 449 rp = found; 450 goto found_entry; 451 } 452 453 if (!rp) { 454 dprintk("nfsd: unable to allocate DRC entry!\n"); 455 goto out; 456 } 457 458 nfsdstats.rcmisses++; 459 rqstp->rq_cacherep = rp; 460 rp->c_state = RC_INPROG; 461 rp->c_xid = xid; 462 rp->c_proc = proc; 463 rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp)); 464 rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp))); 465 rp->c_prot = proto; 466 rp->c_vers = vers; 467 rp->c_len = rqstp->rq_arg.len; 468 rp->c_csum = csum; 469 470 lru_put_end(b, rp); 471 472 /* release any buffer */ 473 if (rp->c_type == RC_REPLBUFF) { 474 drc_mem_usage -= rp->c_replvec.iov_len; 475 kfree(rp->c_replvec.iov_base); 476 rp->c_replvec.iov_base = NULL; 477 } 478 rp->c_type = RC_NOCACHE; 479 out: 480 spin_unlock(&b->cache_lock); 481 return rtn; 482 483 found_entry: 484 nfsdstats.rchits++; 485 /* We found a matching entry which is either in progress or done. */ 486 age = jiffies - rp->c_timestamp; 487 lru_put_end(b, rp); 488 489 rtn = RC_DROPIT; 490 /* Request being processed or excessive rexmits */ 491 if (rp->c_state == RC_INPROG || age < RC_DELAY) 492 goto out; 493 494 /* From the hall of fame of impractical attacks: 495 * Is this a user who tries to snoop on the cache? */ 496 rtn = RC_DOIT; 497 if (!test_bit(RQ_SECURE, &rqstp->rq_flags) && rp->c_secure) 498 goto out; 499 500 /* Compose RPC reply header */ 501 switch (rp->c_type) { 502 case RC_NOCACHE: 503 break; 504 case RC_REPLSTAT: 505 svc_putu32(&rqstp->rq_res.head[0], rp->c_replstat); 506 rtn = RC_REPLY; 507 break; 508 case RC_REPLBUFF: 509 if (!nfsd_cache_append(rqstp, &rp->c_replvec)) 510 goto out; /* should not happen */ 511 rtn = RC_REPLY; 512 break; 513 default: 514 printk(KERN_WARNING "nfsd: bad repcache type %d\n", rp->c_type); 515 nfsd_reply_cache_free_locked(rp); 516 } 517 518 goto out; 519 } 520 521 /* 522 * Update a cache entry. This is called from nfsd_dispatch when 523 * the procedure has been executed and the complete reply is in 524 * rqstp->rq_res. 525 * 526 * We're copying around data here rather than swapping buffers because 527 * the toplevel loop requires max-sized buffers, which would be a waste 528 * of memory for a cache with a max reply size of 100 bytes (diropokres). 529 * 530 * If we should start to use different types of cache entries tailored 531 * specifically for attrstat and fh's, we may save even more space. 532 * 533 * Also note that a cachetype of RC_NOCACHE can legally be passed when 534 * nfsd failed to encode a reply that otherwise would have been cached. 535 * In this case, nfsd_cache_update is called with statp == NULL. 536 */ 537 void 538 nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp) 539 { 540 struct svc_cacherep *rp = rqstp->rq_cacherep; 541 struct kvec *resv = &rqstp->rq_res.head[0], *cachv; 542 u32 hash; 543 struct nfsd_drc_bucket *b; 544 int len; 545 size_t bufsize = 0; 546 547 if (!rp) 548 return; 549 550 hash = nfsd_cache_hash(rp->c_xid); 551 b = &drc_hashtbl[hash]; 552 553 len = resv->iov_len - ((char*)statp - (char*)resv->iov_base); 554 len >>= 2; 555 556 /* Don't cache excessive amounts of data and XDR failures */ 557 if (!statp || len > (256 >> 2)) { 558 nfsd_reply_cache_free(b, rp); 559 return; 560 } 561 562 switch (cachetype) { 563 case RC_REPLSTAT: 564 if (len != 1) 565 printk("nfsd: RC_REPLSTAT/reply len %d!\n",len); 566 rp->c_replstat = *statp; 567 break; 568 case RC_REPLBUFF: 569 cachv = &rp->c_replvec; 570 bufsize = len << 2; 571 cachv->iov_base = kmalloc(bufsize, GFP_KERNEL); 572 if (!cachv->iov_base) { 573 nfsd_reply_cache_free(b, rp); 574 return; 575 } 576 cachv->iov_len = bufsize; 577 memcpy(cachv->iov_base, statp, bufsize); 578 break; 579 case RC_NOCACHE: 580 nfsd_reply_cache_free(b, rp); 581 return; 582 } 583 spin_lock(&b->cache_lock); 584 drc_mem_usage += bufsize; 585 lru_put_end(b, rp); 586 rp->c_secure = test_bit(RQ_SECURE, &rqstp->rq_flags); 587 rp->c_type = cachetype; 588 rp->c_state = RC_DONE; 589 spin_unlock(&b->cache_lock); 590 return; 591 } 592 593 /* 594 * Copy cached reply to current reply buffer. Should always fit. 595 * FIXME as reply is in a page, we should just attach the page, and 596 * keep a refcount.... 597 */ 598 static int 599 nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data) 600 { 601 struct kvec *vec = &rqstp->rq_res.head[0]; 602 603 if (vec->iov_len + data->iov_len > PAGE_SIZE) { 604 printk(KERN_WARNING "nfsd: cached reply too large (%Zd).\n", 605 data->iov_len); 606 return 0; 607 } 608 memcpy((char*)vec->iov_base + vec->iov_len, data->iov_base, data->iov_len); 609 vec->iov_len += data->iov_len; 610 return 1; 611 } 612 613 /* 614 * Note that fields may be added, removed or reordered in the future. Programs 615 * scraping this file for info should test the labels to ensure they're 616 * getting the correct field. 617 */ 618 static int nfsd_reply_cache_stats_show(struct seq_file *m, void *v) 619 { 620 seq_printf(m, "max entries: %u\n", max_drc_entries); 621 seq_printf(m, "num entries: %u\n", 622 atomic_read(&num_drc_entries)); 623 seq_printf(m, "hash buckets: %u\n", 1 << maskbits); 624 seq_printf(m, "mem usage: %u\n", drc_mem_usage); 625 seq_printf(m, "cache hits: %u\n", nfsdstats.rchits); 626 seq_printf(m, "cache misses: %u\n", nfsdstats.rcmisses); 627 seq_printf(m, "not cached: %u\n", nfsdstats.rcnocache); 628 seq_printf(m, "payload misses: %u\n", payload_misses); 629 seq_printf(m, "longest chain len: %u\n", longest_chain); 630 seq_printf(m, "cachesize at longest: %u\n", longest_chain_cachesize); 631 return 0; 632 } 633 634 int nfsd_reply_cache_stats_open(struct inode *inode, struct file *file) 635 { 636 return single_open(file, nfsd_reply_cache_stats_show, NULL); 637 } 638